The present invention relates to golf club shafts, and more particularly to the production of a variety of golf club shafts of varying natural frequency and length from a universal blank shaft of given length.
As presently manufactured, golf club sets are matched by utilizing static determinations including the originator's designation of shaft flex. The flex of a shaft is an arbitrary and relative designation and varies widely within specific flex designations. Generally, flex designation "X" stands for an extra stiff shaft, "S" for a stiff shaft, "R" for a regular shaft, "A" for a semi-flexible shaft, and "L" for a lady or flexible shaft.
Many flex designations are determined by utilizing a flex board which statically measures the deflection of a shaft under the influence of a predetermined test weight secured to the tip end of a shaft anchored at the butt end. In actuality this procedure does not measure the flex or elasticity of the shaft which varies according to cross-section, heat treating processes, metal composition and other such factors. Hence, deflection is the only shaft characteristic measured by this procedure.
The flexibility of a golf club shaft plays an important role in producing desirable golf shots. In connection with this role, it is believed highly desirable that during a golf shot the club shaft travel through a specific number of cycles of deflection from the start of the down swing of the club to its point of impact with the ball. Ultimately, when the club head contacts the ball, it is desirable that the shaft be in an undeflected position which locates the head at its point of maximum velocity.
Strain gage information, however, reveals that it is not possible to strike the ball in the acceleration phase of the golf club head. On a full shot with wood or iron, the ball is impacted during the deceleration phase. The objective, therefore, is to strike the ball as high in the deceleration phase, or as close to maximum velocity of the head as possible. Thus the timing or tempo of the swing must accommodate for the frequency or stiffness of the shaft.
The magnitude of the problem becomes evident when the golfer attempts to use the same swing, tempo, or timing with different golf clubs in a set that is mismatched in frequency or stiffness.
The above considerations clearly show the desirability of a frequency matched set of golf clubs. Utilizing such a set of clubs tailored to the swing of a particular golfer, when the proper pass is placed on each of these clubs, the club head contacts the ball closer to its point of maximum velocity thereby producing a highly desirable golf shot.
Heretofore the inventory of golf club shafts in the manufacture of club sets was quite substantial. Within each of the five categories of flex noted above, nine shaft lengths are required for the irons numbering two through nine and pitching wedge. This ultimately requires an inventory of 45 different shafts. Additionally, for reasons noted above, within each flex category the actual natural frequency of the particular shafts grouped therein greatly varies. Such variations of natural frequency within which each flex category significantly complicate the inventory of shafts necessary to produce frequency matched club sets.